The present invention generally relates to devices and methods for monitoring the performance of an engine, such as an internal combustion engine. More specifically, the invention provides a system for monitoring data related to the engine performance and defining an engine duty cycle.
Owners and operators of power plants, such as internal combustion engines, are continuously faced with the problem of making the most economical use of their engines. This need is particularly keen for automotive engines and the vehicles that they power. Vehicle and engine recording devices have been developed for a variety of applications pertaining to both operator and vehicle communication and control. From the vehicle operator""s standpoint, a recording device can be used to log and report such items as the operator""s driving time, trip time, vehicle and engine faults, and other operating information. With respect to the vehicle itself, the recording device can be used to record fuel efficiency on a trip-by-trip basis, engine operating parameters and other related information.
One such system is depicted in FIGS. 1 and 2. In this prior system, a vehicle monitoring device 10 communicates with an engine/vehicle controller 12 via a communications bus 14. The communications bus is typically according to an industry standard configuration, such as an SAE-J1587 bus. This data bus is preferred in the automotive and trucking industry because it permits communication of a large quantity of data between the controller 12 and the monitoring device 10.
In a typical automotive vehicle, the controller 12 not only controls the function of various components of the engine and vehicle, it also generates data or translates sensor outputs regarding the performance of these components. In one such controller, the CENSE(trademark) system sold by Cummins Engine Company of Columbus, Ind. the data output on bus 14 can include engine speed, engine percent torque, instantaneous engine load, instantaneous fuel rates, as well as data related to the functional elements of the engine such as valve position, fuel injector setting, and the like.
The monitoring device 10 can be mounted within the vehicle, and can include a connector 26 to enable convenient connection with a printer 22. In one embodiment, the device 10 includes a microprocessor or micro-controller 28, a keypad 30, a back light 32 for eliminating an LCD display 34, a DUART asynchronous receiver/transmitter 36 and an audible alarm 38. The majority of the data processed by the micro-controller 28 is received through the communications link 14. However, additional data inputs to the micro-controller can be provided, such as an engine speed signal 40 and a vehicle speed signal 42.
The micro-controller 28 is programmable via the keypad 30 to accumulate and output specific trip data, such as odometer setting and trip mileage, total fuel consumption and mean fuel consumption rate. As a further refinement, the monitoring device 10, and particularly the micro-controller 28, can be programmed to delineate fuel usage and fuel economy as a function of certain specific categories of the vehicle operation. In one mode of operation of the monitoring device 10 shown in FIG. 1, the device generates an audit trail indicative of the overall performance of the vehicle during a particular trip. A sample output of this form is depicted in FIG. 2. In the illustrated embodiment, four such categories can be implemented: drive, in which the vehicle has a non-zero speed; idle, in which the vehicle speed is zero; PTO, in which the vehicle engine is driving an auxiliary component; and a vehicle speed greater than 65 miles per hour (or any other predetermined speed).
The monitoring device 10 provides the information shown in the output of FIG. 2 to allow the vehicle operator/owner to evaluate the vehicle and/or vehicle operator performance. For example, the audit trail shown in FIG. 2 provides information as to the amount of time that the vehicle is running at idle. A lengthy idle period significantly reduces the fuel economy for the vehicle, and is indicative of poor vehicle usage or driving habits of the vehicle operator.
The monitoring device 10 is shown in more detail in U.S. Pat. No. 5,303,163, assigned to Cummins Electronic Company and issued on Apr. 12, 1994, the disclosure of which is incorporated herein by reference. This system presents a significant improvement for a vehicle owner/operator""s ability to maximize the usage and profitability of the vehicle. The configurable monitoring system disclosed in that patent provides a clear indication of the overall performance of the vehicle over particular trips. This information can then be used by the owner/operator to establish performance or operating limits that cannot be exceed by the vehicle operator. Hence, the system 10 can include an alarm 38 which can be activated when the vehicle or engine exceeds or falls below limits that are newly established in view of the prior recorded performance of the vehicle and operator. Thus, the invention of the ""163 patent provides a secure and configurable monitoring device that helps a vehicle owner optimize the overall usage and performance of the subject vehicle.
However, the monitoring device shown in the ""163 patent is focused more on a global levelxe2x80x94i.e., the overall performance of the vehiclexe2x80x94as opposed to a local level concentrating on the overall performance of the individual elements of the vehicle, such as the engine. While the device of the ""163 patent allows the vehicle owner to establish overall vehicle operating parameters, it does not provide a basis for establishing specific operating parameters for specific vehicle components like the engine.
Consequently, there remains a need for a monitoring system that has the capacity for providing meaningful data throughout the entire operation of a specific vehicle component, such as the engine. This need is further expressed within the overall desire to improve the performance of the components, and ultimately its cost efficiency to the vehicle owner/operator.
In order to address this need, the present invention contemplates a system and method for monitoring engine performance, and more particularly for defining a duty cycle specific to the particular engine, vehicle and operator. Preferably, the system contemplates a micro-controller that is separate from, but works in conjunction with, an engine/vehicle controller. The engine/vehicle controller provides control signals to various functional components of the engine and vehicle. In addition, the engine/vehicle controller generates data from sensors and virtual sensors indicative of current operating conditions. The micro-controller of the present invention communicates with the engine/vehicle controller to extract data concerning selected operating conditions.
The engine duty cycle can be defined from an engine performance curve that is a function of two or more engine operating parameters or conditions. In a preferred embodiment, engine torque and speed are used to describe the curve. In one feature of the invention, the engine owner/operator can input data into a micro-controller sufficient to define the curve. Preferably, the torque/speed curve is defined by seven data points.
In one aspect of the invention, the area under the performance curve is segmented into a plurality of sectors, each sector corresponding to a range of values for the two or more engine operating parameters. In the preferred embodiment in which torque and speed are the selected operating parameters, the sectors are bounded by engine speeds enveloping the engine speeds input by the user to define the torque/speed curve. The sectors are further bounded by torque values corresponding to specific percent torque curvesxe2x80x94, e.g., 100, 90, 70, 50 and 30 percent of rated torque. The invention contemplates that the speed and torque boundaries defining the duty cycle sectors can be established to provide sufficient information to gauge the engine (or vehicle) performance throughout its duty cycle. For instance, a greater concentration of sectors may be preferable in certain regions of the duty cycle to provide more precise information about the engine operation.
During operation of the engine/vehicle, the micro-controller obtains current data indicative of the monitored engine operating parameters (torque and speed in the preferred embodiment). This current data is then compared to the range of values defining the duty cycle sectors to determine a target sector within which the current data falls. A duty cycle parameter is associated with each sector that is different from the two or more engine operating parameters and unique to that sector. When the engine operating conditions fall within a target sector, the duty cycle parameter for that sector is updated by the monitoring micro-controller.
In one embodiment of the invention, the duty cycle parameter is cumulative time spent in each duty cycle sector. Thus, in one aspect, each duty cycle parameter can be represented by a counter or a cumulative timer maintained in memory for a corresponding target sector. The micro-controller then increments the counter for the appropriate target sector based upon the current data received from the engine/vehicle controller.
The monitoring micro-controller continuously reads the current engine performance data and updates the appropriate duty cycle parameter over predefined iterations. In one embodiment, each iteration occurs at a one second interval. A long term duty cycle map can then be defined by repeating these iterations many times to generate data for a predetermined number of hours of engine operation. Preferably, the long term map is based upon 60,000 hours of engine operation, which can correspond to the number of hours between engine rebuilds for an industrial or commercial engine/vehicle application.
The invention further contemplates generating a display of the engine duty cycle map. This display can include numeric entries in display cells corresponding to the defined duty cycle sectors. The numeric entries preferably correspond to the accumulated time that the engine operated within each sector. Alternatively, a color-coding scheme can be applied to each display cell, where certain ranges of values for the duty cycle parameters are associated with certain colors. This display can be generated on an independent computer based on duty cycle data downloaded from the vehicle-based micro-controller using a conventional data tool.
Armed with the duty cycle information, the engine/vehicle owner, operator or technician can make educated judgments concerning the performance of the engine. This information can be used to determine whether changes are needed in the engine control routines implemented by the engine/vehicle controller. For instance, the duty cycle information generated by the present invention can clearly illustrate that the engine is operating at certain torque/speed combinations, allowing the engine fueling protocol to be modified for optimum operation at those combinations.
In a further feature of the invention, the duty cycle parameter can be the amount of fuel consumed by the engine within the corresponding target sector. A counter can be maintained in memory associated with each sector that is increased when the sensed engine operating parameters fall within the target sector. Data for the amount of fuel consumed over each monitoring iteration can be extracted from a sensor and virtual sensor data generated by the engine/vehicle controller. The duty cycle can thus be defined in terms of fuel consumption, in lieu of or in addition to the cumulative time parameter. This information can be processed with an eye toward modifying the engine fueling strategy implemented by the engine/vehicle controller.
It is also contemplated that additional data can be stored related to each duty cycle sector. For instance, various performance values can be calculated from current sensor data at each monitoring iteration. Values such as instantaneous and cumulative load and speed factors can be stored in memory and date stamped on each pass through the monitoring cycle.
The preferred embodiment contemplates a long term duty cycle map that is downloaded and analyzed relatively infrequently. The invention provides for additional shorter term duty cycle maps created over a significantly fewer number of monitoring iterations. In a specific embodiment, a short term duty cycle map is created from the same data as the long term map, but for a limited number of operating hours (typically 8 to 1000 hours). The short term maps can be downloaded more frequently for making quick adjustments to the engine control routines, evaluating engine/vehicle operator performance, or determining short term maintenance requirements. In one specific embodiment, two such short term maps are provided that are sequentially filled during the monitoring iterations.
One object of the present invention is to provide a system and method for generating an accurate profile of the duty cycle for an engine/vehicle combination that can be used to monitor engine performance and serve as a foundation for modifying associated control routines. Another object is accomplished by features of the invention that permit definition of the duty cycle as a function of various parameters, such as elapsed time and fuel consumption.
One benefit of the invention is that it provides accurate duty cycle information tailored to the specific engine/vehicle application. Another benefit is that the duty cycle information generated in certain embodiments of the invention can be readily displayed for interpretation and evaluation by vehicle/engine owners, operators or technicians.
Other objects and benefits of the invention will become apparent upon consideration of the following written description together with the accompanying drawings.